Hi Anna,
I have seen it go both ways, some needed it when they didn't purchase and some have bought it and didn't make any claims. But any more I do recommend that my clients purchase it. Most also offer some type of baggage coverage for lost or damaged bags, which can be good.
Make sure for the cancellation if it is for any reason and up to day of departure or just for medical reasons only.. But still for the medical most can not be anything that is pre existing. Plus be aware of the "Act of God" clause and in case the airline goes bankrupt or on strike.
Also if you do cancel last minute and did not purchase the insurance, are you ok with losing that amount of money? But always check the operators cancellation penalties.
You just never know when an accident may happen.
Way all options and make the best choice for you.
Tracy